1. Field of the Invention
The invention relates to an enhanced quieter intra-aortic balloon pump system. More particularly, the invention relates to a muffling device for a vacuum pressure reservoir commonly used in intra-aortic balloon pump systems.
2. Description of the Prior Art
Intra-aortic balloon pump therapy is frequently prescribed for patients who have suffered a heart attack or some other form of heart failure. In such therapy, a thin balloon is inserted through an artery into the patient's aorta. The balloon is connected through a series of thin tubes to a complex apparatus which causes the balloon to inflate and deflate repeatedly in time with the patient's heart beat, thereby assuming some of the load of the heart during the patient's recovery period.
The inflation/deflation apparatus supplies positive pressure for expanding the balloon during an inflation cycle and negative
pressure for contracting the balloon during a deflation cycle. In a conventional prior art apparatus, shown schematically in FIG. 1, an intra-aortic balloon 10 is inserted into a patient's aorta and is connected through small profile catheter 12 and a larger profile extender 14 to an isolator 18 divided by a pliant membrane 20 into an input or primary side 22 and a secondary side 24. The entire volume between membrane 20 and balloon 10 is typically filled with a gas, such as helium, supplied by a gas source 26. A positive pressure reservoir 28 is connected through a solenoid valve 30 to the input or primary side 22 of isolator 18. Similarly, a negative pressure reservoir 32 is connected through a solenoid valve 34 to the input or primary side 22 of isolator 18. The primary side 22 of isolator 18 is also connected through a solenoid valve 36 to a vent or exhaust port 38. A compressor 11 is connected to both positive pressure reservoir 28 and negative pressure reservoir 32. By pumping the gas into pressure reservoir 28 and out of negative pressure reservoir 32 at a predetermined rate, compressor 11 assures that positive pressure reservoir 28 is available, at the necessary capacity, for each inflate cycle of balloon 10 and that negative pressure reservoir 32 is available, at the necessary capacity, for each deflate cycle of balloon 10.
During an inflation cycle, solenoid valve 30 is opened to permit positive pressure from positive pressure reservoir 28 to enter primary side 22 of isolator 18. This positive pressure causes membrane 20 to move toward secondary side 24, thereby forcing the helium in the secondary side to travel toward and inflate balloon 10. For deflation, solenoid valve 30 is closed and solenoid valve 36 is opened briefly to vent the gas from primary side 22, after which valve 36 is closed. Solenoid valve 34 is then opened, whereupon negative pressure reservoir 32 creates a negative pressure on the primary side 22 of isolator 18. This negative pressure pulls membrane 20 toward primary side 22, whereby the helium is drawn out from the balloon. Compressor 11 continuously replenishes the positive pressure in positive pressure reservoir 28 and the vacuum in negative pressure reservoir 32.
It is desirable in intra-aortic balloon pump therapy to inflate and deflate the balloon as rapidly as possible. Rapid cycling permits the therapy to be performed more effectively, and enables smaller diameter catheters to be used, thereby reducing the possibility of limb ischemia. Although the prior art system described above permits rapid inflation and deflation cycles, the configuration of this system, specifically the burst of air flow into vacuum reservoir 32 upon the activation of the solenoid valve 34, creates an undesirable “rushing” sound. The vacuum reservoir of the present invention includes a honeycomb structure positioned perpendicular to the jet flow, which spreads the gas stream evenly across vacuum reservoir 32 and reduces the above mentioned “rushing” sound.
Mufflers typically are designed in one of three ways: with staggered baffles, with sound defeating angles or with fiberglass packing. Unlike traditional mufflers, the above mentioned honeycomb structure, does not create significant flow restrictions. Various devices for directing and muffing airflow are known, but the inventors are not aware of any prior use of a honeycomb or similar structure as a muffler; more specifically, the inventors are not aware of any prior incorporation of a honeycomb or other flow straightening structure into a vacuum reservoir for muffling purposes.
While present day intra-aortic balloon pump systems, vacuum reservoirs, and mufflers in general may be suitable for the particular purposes employed, or for general use, they are not as suitable for the purposes of the present invention as disclosed hereafter.